In the industrial world, panel and machine builders use many push buttons and signal lights. These buttons, lights, panels, closets and the like are identified by various means. One such means is hard-plastic identification shields. These shields typically consist of a rectangular, hard-plastic plate that can be plotted, engraved or preprinted by the supplier. “Hard-plastic” means that the plate is stiff and exhibits little, if any, flexibility. The shields or plates are either self-adhesive or mechanically mounted on or about the panel, closet, button, etc. Often these shields are used in combination with a shield or plate holder.
The use of hard-plastic identification shields has a number of disadvantages. If the shields are to be kept in stock, then this can result in the creation and maintenance of a large shield inventory, especially if the shields vary in color, legend and size. If the shields are to be created as needed, then expensive and often operationally slow plotting, and/or engraving equipment must be acquired and maintained (options that are often economical only for large panel applications). Outsourcing the task of creating plotted and/or engraved plates can also be expensive and time consuming.
One alternative to hard-plastic identification shields is a printable label that can be processed in standard printing equipment. Typically, the labels are attached to a carrier strip, fed into a printer, and imprinted with a legend. The labels are then removed from the carrier and attached to or about the objects requiring identification. Because of the limitations of the printers, theses labels tend to be thin and flexible and thus lack the feel and appearance of hard-plastic identification shields. However, printable labels are a well-recognized solution to the problems associated with hard-plastic identification shields, particularly with respect to cost and inventory.
One particularly useful class of printers for creating printed labels is the type that employs thermal transfer (THT) printing technology. Of these printers, hand-held THT printers are particularly desirable due to their low cost (relative to desktop printers), portability and ease-of-use. THT printing uses a heat generating print head to transfer an ink layer (typically a wax and/or other binder compounded with carbon black and/or other pigment) or the like, from a THT ribbon to a label. By using digital technology, characters are formed on a label by energizing a sequence of pixels on the print head and when the print head comes in contact with the ribbon, it softens the wax and/or other binder of the ink layer on the ribbon. At the same time that the print head is in contact with the ribbon, the ribbon is in contact with the label, and thus the character image on the print head is transferred to the label.
THT label printers use a labeling media that is fed from a media unwind simultaneously when a platen roll feeds it and an ink transfer ribbon. The labeling media and the transfer ribbon pass between the print head and the platen, driven by the rotating platen. As a result, the labeling media and the transfer ribbon pass together in overlay relationship between the print head and the platen roll. These printers and their operation are described more fully in U.S. Pat. Nos. 5,951,177, 6,113,293 and 6,769,825.
The use of thick, i.e., greater than (>) about 300 microns (μm), labeling media in many commercially available THT printers, particularly hand-held printers, is problematic at best. Most commercially available THT printers are designed to process labeling media no thicker than about 300 μm, and such labels are far removed from the hard-plastic shields in terms of appearance and feel (or heft). Accordingly, the labeling industry has a recognized need for labels that have the appearance and feel of hard-plastic identification shields but that can be printed using a THT printer, particularly a hand-held THT printer.